The invention relates to data storage media. In particular, the invention relates to techniques for monitoring the position of data recording tape.
The capacity to detect the position of one or more edges of data recording tape, such as magnetic tape is useful many circumstances. For example, data about edge positions are useful in research and development of data recording tape and also devices that use such tape. Edge data are also useful in manufacturing and quality control. Devices that use data recording tape may employ edge data in several ways, e.g., as part of a diagnostic tool, as an indication that the tape is departing from the ideal tape path or as an indication that the tape has become damaged in use.
In one embodiment, the invention provides a system that includes a source of collimated light, such as a laser, and data recording tape that is substantially opaque to the light. The tape may be magnetic tape. The tape is positioned to block a portion of the collimated light. The system also includes a detector, such as a photodiode, configured to detect the light and to generate a signal based upon the detection. The signal from the detector is a function of the position of an edge of the tape. The system may include a pair of sources of collimated light and detectors to generate two signals dependent upon the positions of opposing edges of the tape. These signals may be added, subtracted or otherwise processed to generate additional useful signals. The signals provide indications of tape edge position or other tape data that are generally insensitive to changes in the tape plane.
In other embodiments, the invention provides methods for processing signals that are a function of the edge positions of tape.
In a further embodiment, the invention presents a method for generating a function that relates the signals to the edge positions.
Other advantages, features and embodiments of the present invention will become apparent from the following detailed description and from the claims.